CN101803016A - methods for attachment and devices produced using the methods - Google Patents

Abstract

Methods for attachment and devices produced using such methods are disclosed. In certain examples, the method comprises disposing a capped nanomaterial on a substrate, disposing a die on the disposed capped nanomaterial, drying the disposed capped nanomaterial and the disposed die, and sintering the dried disposed die and the dried capped nanomaterial at a temperature of 300 DEG C or less to attach the die to the substrate. Devices produced using the methods are also described.

Description

Attachment method and devices produced using this method

related application

This application claims priority and the benefit of U.S. Patent Provisional Application No. 60/950,797, filed July 19, 2007, and U.S. Patent Application No. 12/175,375, filed July 17, 2008, which are hereby incorporated by reference The entire disclosure of each application is incorporated.

field of invention

Certain embodiments disclosed herein generally relate to methods of attaching electronic components to substrates. More specifically, certain embodiments are directed to methods of attaching die using temperatures less than or equal to 300°C and devices fabricated using such methods.

Background technique

In attaching the die to the substrate, contacts or electrical bonds are used between the die and the substrate. In preparing the joints, high temperatures in excess of 300°C may be used. Such high temperatures can damage the sensitive die, resulting in poor device performance or limited lifetime.

Contents of the invention

Certain features, aspects and embodiments described below are directed to functional and/or operational junctions at temperatures of 200°C or higher. Because tin is a low melting point metal, conventional solders, usually tin alloys, will fail quickly at this temperature. The joint embodiments described herein are able to operate at such high temperatures by including silver that melts at 900°C. In some aspects, a procedure of sintering silver nanopowder with a specific amount of capping agent at a temperature below 300°C may be used to provide a joint. As discussed further below, the selected amount of capping provides high density silver contacts and prevents cracking of the silicon die during pressure sintering.

In a first aspect, a method of attaching an electronic component to a substrate is disclosed. In a particular embodiment, the method comprises disposing a capped nanomaterial on a substrate, disposing an electronic component on the disposed capped nanomaterial, drying the disposed capped nanomaterial and the disposed electronic composition, and Sintering the dried arranged electronic components and the dried capped nanomaterials at a temperature below 300°C to attach the electronic components to the substrate. In some embodiments, the electronic component may be a die.

In particular embodiments, the capped nanomaterial may comprise silver particles capped with a capping agent, wherein the capping agent is based on the weight of the capped silver particles in an amount of about 0.2 wt.% to about 15 wt.%, more specifically Say about 1.5-2.5 wt.% occurs. In some embodiments, the method may further comprise dispersing the capped silver particles in a solvent prior to disposing the capped silver particles on the substrate. In other embodiments, the method may further include removing the capping agent from the capped silver particles during the sintering step. In some embodiments, the capped nanomaterial may comprise capped metal particles, wherein the metal of the capped metal particles is selected from the group consisting of gold, silver, copper, nickel, platinum, palladium, iron, and alloys thereof. In a particular embodiment, both the drying and sintering steps are done below 300°C. In some embodiments, the sintering step may be done in a nitrogen atmosphere. In a particular embodiment, the nitrogen atmosphere provides a pressure substantially equal to atmospheric pressure. In other embodiments, the pressure may be above atmospheric pressure, for example, from about 0.2-20 MPa or about 5 MPa. In other embodiments, the drying step may be accomplished at subatmospheric pressure.

In another aspect, there is provided a device comprising a substrate, an electronic component arranged on the substrate, and an electrical contact between the electronic component and the substrate, wherein the electrical contact comprises sintering at a temperature of 300° C. or lower to provide the substrate and the electronic component. Nanomaterials with electrical connections between components. In certain embodiments, the electronic component may be a die.

In a particular embodiment, the substrate may be a printed circuit board and the nanomaterial comprises capped silver particles. In some embodiments, the capped silver particles comprise from about 1 wt.% to about 15 wt.% capping agent based on the weight of the capped silver particles prior to forming the joint. In other embodiments, the nanomaterial may comprise metal particles, wherein the metal of the metal particles is selected from the group consisting of gold, silver, copper, nickel, platinum, palladium, iron and alloys thereof. In some embodiments, the electrical contacts may have a substantially uniform thickness between the die and the substrate. In certain embodiments, the electrical contacts may be substantially void-free.

In an additional aspect, a kit for producing electrical contacts is disclosed, the kit comprising capped metal particles comprising from about 1 wt. % to about 15 wt. % capping agent based on the weight of the nanomaterial Nanomaterials and instructions for using the nanomaterials to provide electrical contacts between a substrate and electronic components disposed on the substrate.

In certain embodiments, the kit may further include an electronic component, for example, a die, for use with the nanomaterial. In other embodiments, the kit may further include a matrix for use with the die and nanomaterial. In some embodiments, the substrate may be a printed circuit board.

In another aspect, there is provided a method of facilitating electrical bonding of an electronic component and a substrate, the method comprising providing a nanomaterial that provides a nanomaterial between the electronic component and the substrate after sintering the nanomaterial at a temperature of 300° C. or less. Effective for electrical contacts. In certain embodiments, the electronic component may be a die.

In certain embodiments, nanomaterials may be effective to provide an electrical contact between the electronic component and the substrate after sintering at sub-atmospheric pressures. In some embodiments, the nanomaterial comprises capped silver particles with about 1 wt.% to about 15 wt.% capping agent based on the weight of the capped silver particles. In some embodiments, the nanomaterial may comprise metal particles, wherein the metal of the metal particles is selected from the group consisting of gold, silver, copper, nickel, platinum, palladium, iron and alloys thereof. In other embodiments, the metal particles may be capped with capping agents selected from thiols and amines.

Additional aspects, embodiments, examples and features are described in more detail below.

Description of drawings

Certain illustrative embodiments, features, and aspects will be described in more detail below with reference to the accompanying drawings, in which:

1A-1D are schematic diagrams of a method of creating an electrical contact between an electronic component and a substrate according to certain embodiments;

2-2E are schematic illustrations of another method of creating an electrical contact between an electronic component and a substrate in accordance with certain embodiments;

Figure 3 is an X-ray photograph of a die attached to a copper heat spreader in accordance with certain embodiments;

4 is an SEM image showing a cross-section of a nanosilver contact according to certain embodiments.

The dimensions of certain elements in the drawings have been intentionally distorted, enlarged or reduced relative to the dimensions of other elements in the drawings to facilitate a better understanding of the techniques described herein. For example, the thickness of the contacts, the size of the electronic components and/or the size of the substrate have been intentionally shown out of proportion to each other in order to provide a more user-friendly depiction. Illustrative dimensions and thicknesses of the components shown in the figures are described in more detail below.

Detailed ways

Certain embodiments described herein are directed to attaching electronic components (including but not limited to dies) to selected substrates (or certain regions thereof) (including but not limited to pre-pregs, printed Materials and devices on circuit boards or other substrates commonly used in the production of electronic devices.

In a typical die attach procedure, a silicon die is attached and electrically connected to a substrate before being protected by encapsulation or encapsulation. In order to avoid damage to the device, the attachment temperature is usually below 300°C. There are two types of die attach materials that are widely used in electronics packaging today: solder alloys and resin-based composites. Both materials have low processing temperatures and relatively low thermal and electrical conductivity. Dies bonded with these materials perform reliably at operating temperatures below 125°C. For higher operating temperatures, the die is typically bonded using a high temperature solder (ie, AuSn) or a silver-glass containing composite. These materials require high processing temperatures, generate high mechanical stress in the device, and these materials have relatively low thermal and electrical conductivity.

Silver has high electrical and thermal conductivity and is an attractive die attach material that can replace solder alloys and composites for packaging power semiconductors. While the operating temperature of solder is limited by its melting point, sintered silver joints can be used above the sintering temperature, allowing high performance devices to operate at high temperatures. Micron-sized and nano-sized silver powders are used to formulate printing pastes for die attach. Devices assembled with silver paste demonstrated high reliability in power electronics applications. A typical attachment procedure involves Ag paste stencil printing followed by sintering at a temperature of ~300°C and a pressure of about 30-40 MPa. The applied pressure is essential to ensure the sintering of the silver powder at such low temperatures and to provide good Ag bonding to the substrate interconnect. Applying such high pressure complicates the attachment procedure and may damage the silicon device.

Certain features, aspects, and embodiments disclosed herein are directed to utilizing specially formulated nanomaterials (e.g., nanosilver paste) and allowing electronic components (e.g., silicon dies) to operate at temperatures of 300° C. or less and/or in Attachment procedure to a substrate at zero or subatmospheric pressure. These materials are referred to below in certain instances as "nanomaterials". Illustrative nanomaterials are disclosed in commonly assigned US Patent Application Serial No. 11/462,089, filed August 3, 2006, the entire disclosure of which application is hereby incorporated by reference. Nanomaterials suitable for use in the devices and methods described herein may include one or more types of metal particles capped with a selected amount of capping agent.

In certain embodiments, the use of a monophasic solution to produce microparticles for use in the attachment procedure allows for the omission of phase transfer reagents commonly used to produce microparticles in polyol procedures (although phase transfer reagents may still be used in certain embodiments). By carrying out the reaction in a single phase, the ease of producing the microparticles is increased while the cost of producing the microparticles is reduced. In addition, large-scale industrial microparticle synthesis may be achieved using single-phase reactions. Additional benefits of particles and methods of producing them will be readily selectable by those skilled in the art after being prompted by this disclosure.

According to certain embodiments, the metals used to provide the particles used in the attachment procedure may be uncomplexed or complexed with one or more ligands. For example, metals may react with EDTA, ethylenediamine, oxalate, 2,2′-bypyridine, cyclopentadiene, diethylenetriamine, 2,4,6-trimethylbenzene Group-1,10 o-phenanthroline, triethylenetetramine or other ligands. In certain embodiments, the metal or metal salt may be dissolved in a solvent or solvent system to provide a clear but not necessarily colorless solution. For example, an appropriate amount of metal or metal salt may be added to the solvent such that when the metal or metal salt comes into solution, the overall solution is clear. The entire solution may be colored or colorless. Suitable solvents include, but are not limited to, ethylene glycol, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isoamyl alcohol, hexanol, and fatty acids having from about 1 to about 10 carbon atoms alcohol. Other suitable solvents include, but are not limited to, benzene, toluene, butene, polyisobutylene, Isopar(R) solvents commercially available from Exxon, and aromatic compounds with aliphatic branching containing 2-6 carbon atoms. Suitable solvent systems include mixtures of the illustrative solvents discussed herein and other fluids that are soluble, miscible, or partially miscible with such illustrative solvents. In particular embodiments, the combination of solvents provides a single phase. To achieve a single phase when mixed solvents are used, the amounts of each solvent can be adjusted so that a single phase results when the solvents are mixed. In cases where more than one phase appears after mixing, the relative amounts of one or more solvents can be varied (eg, increased or decreased) until a single phase is observed.

According to certain embodiments, metal particles may be mixed with capping agents. Capping agents may be effective in sequestering microparticles and limiting the size of their growth. In certain embodiments, the capping agent may be a high molecular weight capping agent, for example, having a molecular weight of at least about 100 g/mole. Illustrative capping agents include, but are not limited to, organic amines having more than 12 carbon atoms. In particular embodiments, the organic amine has at least 16 carbon atoms, for example, hexadecylamine. The organic portion of the amine may be saturated or unsaturated, and may optionally include other functional groups, for example, thiol, carboxylic acid, polymer, and amide. Another illustrative group of capping agents suitable for use with the metals of the materials disclosed herein are mercaptans having more than 12 carbon atoms. In particular embodiments, the thiol has at least 6 carbon atoms. The organic portion of the thiol may be saturated or unsaturated, and may optionally include other functional groups, for example, pyrrole and the like. Another group of capping agents suitable for use are pyrimidine-based capping agents, eg, triazolopyridine, terpyridine, and the like. If prompted by this disclosure, other suitable capping agents will be readily selected by those originally skilled in the art.

In certain embodiments where a capping agent is used in conjunction with the metal particles to provide the material for the attachment procedure, the capping agent may be dissolved in a suitable solvent prior to addition to the metal solution. For example, the capping agent may first be dissolved in a solvent, and this solution is then mixed with the metal solution. In other embodiments, the capping agent may be added directly to the metal solution as a solid or liquid without first being dissolved in a solvent. The capping agent may be added, for example, in incremental steps, or it may be added in a single step. In particular embodiments, the precise amount of capping agent added to the metal solution may vary, depending on the desired properties of the resulting capped particles. In some embodiments, adding an appropriate amount of capping agent provides a desired amount of capping agent by weight in the capped microparticles. The expected weight of such capping agents for materials useful in the attachment procedure is discussed in more detail below. Those of ordinary skill in the art, given the reminder of this disclosure, will recognize that it may be desirable to use more or less capping agents depending on the desired properties of the resulting material. For example, to increase the conductivity of particles disposed on a substrate (eg, a printed circuit board), the amount of capping agent is adjusted until the conductivity (or other physical property) reaches an optimum value or falls within a desired range Inclusion may be desirable. The selection of an appropriate capping dose will be within the ability of those originally skilled in the art, if prompted by this disclosure.

In certain embodiments, when the capping agent (or capping agent solution) and the metal salt solution are mixed, a single phase is created or maintained. In alternative embodiments, the metal salt solution may be a single phase prior to the addition of the capping agent or solution of the capping agent and remain a single phase after the addition of the capping agent or solution of the capping agent. Alternative embodiments in which the metal solution and capping agent are combined to provide a single phase would be readily selected by one of ordinary skill in the art, given this disclosure. In certain embodiments, the capping agent and metal solution may be mixed using conventional techniques (eg, stirring, sonication, agitation, vibration, shaking, etc.). In some embodiments, the capping agent may be added to the metal solution while stirring the metal solution. In certain examples, the mixture of capping agent and metal solution may be stirred until a clear and/or colorless single-phase solution results.

According to certain embodiments, the reducing agent may be added to the metal-capping agent solution either before or after deposition on the substrate. Suitable reducing agents include agents capable of converting dissolved metal ions in solution into metal particles which will precipitate out of solution under selected conditions. Illustrative reducing agents include, but are not limited to: sodium borohydride, lithium aluminum hydride, sodium cyanoborohydride, potassium borohydride, sodium triacetoxyborohydride, sodium diethylaluminate, tri- or tetrabutoxyhydrogen Sodium aluminate, sodium bis(2-methoxyethoxy)aluminate dihydrogenate, lithium hydride, calcium hydride, titanium hydride, zirconium hydride, diisobutylaluminum hydride (DIBAL-H), dimethylsulfide boron Dimethylsulfide borane, ferric ion, formaldehyde, formic acid, hydrazine, hydrogen, isopropanol, phenylsilane, polymethylhydridosiloxane, potassium ferricyanide, silane, sodium sulfoxylate, sodium amalgam , sodium (solid), potassium (solid), sodium dithionite, stannous ions, sulfite compounds, tin hydride, triphenylphosphine, and zinc-mercury amalgam. The exact amount of reducing agent added to the metal-capping agent solution may vary, but usually the reducing agent is added in such excess that substantially all of the dissolved metal is converted from a charged to an uncharged state, for example, Ag ⁺¹ may be converted to Ag ⁰ or Cu ⁺² may be converted to Cu ⁰ . In some embodiments, the reducing agent may be dissolved in the solvent prior to addition to the metal-capping agent solution, while in other embodiments, the reducing agent may be added directly to the metal-capping agent solution without prior dissolve. When a solvent is used to dissolve the reducing agent, the solvent is preferably non-reactive such that the solvent is not altered or altered by the reducing agent. Illustrative solvents suitable for use with reducing agents include, but are not limited to, tetrahydrofuran (THF), N,N-dimethylformamide (DMF), ethanol, toluene, heptane, octane, and solvents having six or more carbon atoms. The solvent is, for example, a linear, cyclic or aromatic solvent having six or more carbon atoms. If prompted by this revelation, those already familiar with the art will be able to select suitable solvents for dissolving the reducing agent.

According to certain embodiments, the reducing agent and capping agent-metal solution may be mixed or stirred for a sufficient time to allow the reducing agent to react with the metal. In some embodiments, agitation may be accomplished at room temperature, while in other embodiments, agitation or mixing is accomplished at elevated temperatures (eg, from about 30°C to about 70°C), for is the accelerated restore program. When using elevated temperatures, it may be desirable to reduce the probability of solvent evaporation by maintaining the temperature below the boiling point of the solvent or solvent system, although in some embodiments it may be desirable to reduce the overall volume of solvent. need.

According to certain embodiments, metal particles may be segregated from a single-phase solution prior to deposition on the substrate. Isolation may occur, for example, by decanted, centrifuged, filtered, sieved or addition of another liquid in which the capped metal particles are not soluble, for example, by extraction. For example, liquids like methanol, acetone, water or polar liquids may be added to organic solutions obtained from adding metal salts, capping agents and reducing agents to organic solvents or organic solvent systems. In certain embodiments, multiple separate additions of extraction liquid may be applied to the solution to remove capped metal particles. For example, a first amount of extract may be added to remove some metal particles. This first quantity of extract may then be removed, decanted or otherwise separated from the organic solution, after which another quantity of extract may be added to the organic solution. The exact amount of extraction solution used to isolate the metal particles may vary depending on the volume of solvent used to produce the capped metal particles. In some embodiments, about two to four times or more solvent is used to extract the capped metal particles, for example about 20 liters or more may be used if the metal particles are produced in about five liters of solvent more extracts. The selection of the proper solvent and the proper amount of solvent will be within the ability of one originally skilled in the art, given the prompting of this disclosure.

According to certain embodiments, capped microparticles may be separated from the extract using conventional techniques (eg, decantation, centrifugation, filtration, etc.). In some embodiments, the extraction solution may be evaporated, leaving capped microparticles. The capped microparticles may be washed, sized, heated, or otherwise treated before, during, or after separation from the extract. In certain embodiments, the extract may optionally be used as a carrier fluid, as discussed in more detail herein, along with one or more solvents, to provide the ink. In other embodiments, the capped metal particles may remain in a single phase solution, and the particles may be arranged on a silicon substrate (or other suitable substrate), for example, according to a pattern, shape or pattern on the substrate. The high temperature of the sintering process results in evaporation of the solvent and sintering of the metal particles, which can provide metallic bonds to enhance the adhesion of the conductor to the substrate.

According to certain embodiments, the capped microparticles may be dried to remove any residual liquid. For example, the capped microparticles may be oven dried, may be dried using vacuum, or may be subjected to freeze drying to otherwise remove any residual extractant and/or solvent. Dry capped microparticles may optionally be stored at room temperature in a sealed container to avoid moisture ingress. In alternative embodiments, a separate drying step may be omitted, and the particles may be dried during the sintering procedure.

According to certain embodiments, the capped microparticles may be treated to remove the capping agent prior to use. Capping agents typically remain on the surface of the microparticles after reaction, but the presence of capping agents can be undesirable. For example, where it is desired to use the microparticles with the lowest possible level of organic contamination, it would be advantageous to remove the capping agent from the capped microparticles. In particular embodiments, the capped microparticles may be treated until the level of capping agent is reduced below about 2% by weight, more specifically below about 1% by weight, for example, capping agent The terminal agent is present at about 1.5-2.5% by weight. In some embodiments, the capping agent may be removed to provide a substantially pure metal, such as substantially pure silver, which may be deposited on the substrate.

In particular embodiments, the exact metal used to provide the nano-ink may vary, for example, conductive metals or conductive metal salts including but not limited to transition metals or transition metal salts, gold, silver, Copper, nickel, platinum, palladium, iron and their alloys. The exact form of the metal or metal salt may vary, depending on the solvent system chosen. It is desirable for the metal salt to dissolve in the selected solvent system without undue heating which might cause the solvent to evaporate. Illustrative anions of metal salts include nitrate, chloride, bromide, iodide, thiocyanate, chlorate, nitrite, and acetate. If prompted by this disclosure, other metal salts suitable for producing nanoinks suitable for attaching electronic components to substrates will be readily selected by those originally skilled in the art.

Particular embodiments of capping materials used herein are selected to include a desired amount of capping agent so that handling of the material does not adversely affect the resulting final product or electrical contacts. For example, the amount of capping agent may be selected to provide a joint or bond with low void volume, high conductivity, and few or no discontinuities. For example, certain embodiments disclosed herein take advantage of the advantageous characteristics of capped materials with selected amounts of capping agents to wet and bond solid surfaces during sintering procedures at temperatures of 200-300°C.

In certain embodiments where a capping material is used in the attachment procedure, the weight percent capping agent in the material may vary depending on the type of capping agent and/or joint desired. For example, materials with little or no capping agent are unlikely to adhere effectively to a substrate material such as silicon. Sintering of structures formed from capped materials with levels of capping agent that are too low can be difficult without the application of appreciable external pressure. Too much capping agent may also have an undesired effect on the resulting joint. For example, if the amount of capping agent is too high, rapid release of organic species during sintering may cause the sintered structure to be porous and mechanically weak. In embodiments using hexadecylamine (HDA), the level of capping agent in the resulting material may be about 10-14 wt.%. Where other capping agents are used, the weight percent capping agent may vary, with illustrative ranges being approximately 1-10% by weight for pyrimidine-based capping agents and approximately 1-10% by weight for thiol-based capping agents. 1-15%.

In certain embodiments, the nanomaterials described herein may be used to provide an electrical contact between an electronic component (eg, a die) and a substrate. A first illustrative method is shown in Figures 1A-1D. For purposes of illustration only, the electronic components shown in the figures refer to dies, although other suitable electronic components may also be used, as discussed further below. Referring to FIGS. 1A and 1B , nanomaterials 110 are arranged on a substrate 100 . As used herein, "arranging" means depositing, coating, brushing, painting, printing, screen printing or otherwise placing one material on another material or substrate. The exact method used to arrange the nanomaterials may vary, and illustrative methods include, but are not limited to, inkjet printing, stencil printing, coating, brush coating, spin coating, vapor deposition, and the like. In some instances, the entire surface of the substrate may be coated with a layer of nanomaterial, one or more die may be placed in the desired location and excess material may be later removed or etched away from the substrate. In other embodiments, nanomaterials may only be placed in selected areas of the intended die attach site.

In certain embodiments, the nanomaterials may be arranged on the substrate to a thickness of from about 10 microns to about 200 microns, more specifically from about 25 microns to about 75 microns. Nanomaterials may be arranged at a substantially uniform thickness, or certain regions may have increased (or decreased) thickness compared to other regions. For example, it may be desirable to select a first thickness for attachment of a first type of electronic component to the substrate and a second thickness for attachment of a different type of electronic component to the substrate.

In some embodiments, a flux or other material may be deposited on the substrate prior to disposing of the dye in order to remove any oxidation from the surface of the substrate during processing of the composition, illustrative fluxes include, but are not limited to, their The entire disclosure incorporates those described in commonly assigned PCT Application No. PCT/US2007/81037, entitled "Flux Formulation." However, in other embodiments, the nanomaterial itself has suitable properties for removing oxidation (or preventing oxidation from occurring) from the substrate surface such that flux or other materials are not required.

Illustrative dimensions of substrates suitable for use with the methods and kits disclosed herein include, but are not limited to, having a length of about 0.1 cm to about 2 cm, a width of about 0.1 cm to about 2 cm, and a width of about 0.01 mm to about 0.5 mm. those of thickness. Dies used in the procedures and kits disclosed herein generally include semiconducting material (or other conductive material) that may be placed on selected portions of a substrate. Dies may be produced, for example, by providing a plurality of dies, each containing one or more integrated circuits, using suitable wafer fabrication processes including, but not limited to, wafer mounting and semiconductor die dicing. Illustrative other electronic components that may be attached using the materials and devices disclosed herein include, but are not limited to, copper heat spreaders, silver or gold wires, LEDs, MEMS, and other components that may be attached to circuit boards or substrates.

After the nanomaterial 110 is arranged, the electronic component 120 can be arranged on the arranged nanomaterial 110 (see FIG. 1C ). Such arrangements may use manual placement, automated pick-and-place equipment, or other suitable means of placing electronic components at the desired locations or areas on the printed circuit board. The electronic component 120 is typically placed on the arranged nanomaterial 110 without the use of external force or pressure. Electronic composition 120 may be suitably held in contact with nanomaterial 110 prior to sintering.

After electronic component 120 is arranged, the entire assembly may be sintered such that nanomaterial 110 solidifies, providing an electrical contact between electronic component 120 and substrate 110 (see FIG. 1D ). During the sintering process, the thickness of the nanomaterial 110 generally decreases. Desirably, sintering is accomplished at a temperature that provides a suitable electrical contact but is not so high as to possibly damage the electronic components. For example, the nanomaterials described herein allow sintering at temperatures below 300° C. to provide electrical contacts of substantially uniform thickness with little or no voids. By using temperatures below 300°C, potential damage to electronic components is reduced. Sintering may occur by heating the entire assembly or by focusing heat on specific electronic component-nanomaterial-matrix sites. In some embodiments, the entire device may be placed in an oven. Other devices suitable for sintering include, but are not limited to, copper heat spreaders, silver or gold wires, LEDs, MEMS, and the like. In some embodiments, sintering may be accomplished at a pressure of about 0.2-20 MPa (eg, about 5 MPa).

In certain embodiments, the assembly may be sintered for a selected period of time using a selected temperature profile. The temperature profile for sintering may be a linear, stepped or other suitable temperature profile. For example, during the sintering step, the temperature may be cycled multiple times between a first sintering temperature and a second sintering temperature. As a result of the sintering, an electronic assembly 150 (FIG. ID) is produced, wherein the assembly includes the electronic component 120, the substrate 110 and the electrical contact 140 therebetween. The electronic assembly may undergo further processing including, but not limited to, placing additional electronic components on the substrate, heating, drying, further sintering, and other processing steps commonly implemented in the production of electronic devices (e.g., printed circuit boards) .

In certain embodiments, one or more drying steps may be implemented during production of the assembly. Drying may be used, for example, to remove solvents and surfactants prior to the sintering step. Drying may be done before placing the die on the substrate or after placing the die on the substrate. For example, referring to FIGS. 2A-2E , electronic components may be produced by arranging nanomaterials 220 on a substrate 210 . Such arrangements may be made using any of the illustrative methods disclosed herein or other suitable methods. Although not shown, the substrate may be dried prior to placement of the electronic components shown at 230 . Electronic components 230 may be arranged on nanomaterials 220 (see FIG. 2C ). The electronic component-nanomaterial-matrix assembly may optionally be dried at a suitable temperature using a suitable device (see Figure 2D). Component 240 may then be sintered at a sintering temperature to provide sintered component 250 .

In certain embodiments, the drying temperature may vary from about 5°C to about 200°C, more specifically from about 120°C to about 160°C, and is generally lower than the sintering temperature. Hot air dryers, ovens, IR lamps, hot plates, and other devices that provide heat may be used to dry the ingredients. In some embodiments, the assembly may be dried in an oven at a first temperature and then sintered in the same oven at a second temperature. In other embodiments, drying may be accomplished at subatmospheric pressures. In some embodiments, two or more drying steps may be performed. For example, the first drying step may be performed at a first temperature, e.g., the substrate may be dried prior to placing the electronic components on the substrate, and then heated at a temperature higher or lower than that of the first drying step. A second drying step is performed at a second temperature of .

In certain embodiments, by drying and sintering the electronic component, little or virtually no voids may be present in the sintered nanomaterial. Formation of voids in nanomaterials can reduce the overall integrity of electrical contacts and lead to poor performance. In some embodiments, subatmospheric pressures may be used to further reduce the possibility that voids may form.

Certain specific embodiments are described in greater detail below in order to further illustrate some of the novel features of the technology described herein.

Example 1

Nanosilver pastes containing capped silver particles were prepared as described in US Patent Application Serial No. 11/462,089. Briefly, the composition of the silver paste was 80 wt.% nano silver powder with cetylamine capping agent in an amount ranging from 0 to 15 wt.%. Butyl carbitol was used as solvent (19.5 wt.% in the slip) and the surfactant BYK163 (0.5 wt.% in the slip) was also present. The composition was first mixed for 1 minute at 2500 rpm in a high-speed mixer SpeedMixer DAC 150FVZ-K and then ground in a 3-roller mill from EXAKT. The resulting material is used to wet and bond solid surfaces at temperatures of 200-300°C during the sintering process.

Experiments done using nanosilver powders with different amounts of cetylamine capping agent showed that nanomaterials containing no or minimal amount of capping agent did not adhere to silicon or any other material. It also cannot be sintered into a dense structure without applying considerable external pressure. Experiments performed using nano silver powders with high capping agent content (for example, above 10 wt.%) also provided undesirable results. In the case of high capping agent content, the rapid release of organic species during sintering may cause the sintered structure to be porous and mechanically poor.

Through experiments, it was found that for hexadecylamine (HAD) capped nano-silver powder, the desirable amount of capping agent to provide desirable properties was at about 1.5-2.5wt.% based on the weight of capped nano-silver powder. In the range.

Example 2

Prepare the slurry, which has the following ingredients: 70wt.% nano-silver powder (based on the weight of the blocked nano-silver powder with 2wt.% HDA capping), 15wt.% butyl carbitol, 2wt.% toluene, 0.75wt. % dispersant Dysperbyk 163 and 0.5wt.% wetting agent Sylquest A1100.

The paste was stencil printed onto a 25 mm x 25 mm alumina direct bonded copper (DBC) substrate from Curamic Electronics. The stencil thickness is 150 microns and the opening is 20 x 20 mm. A 15 x 15 mm silicon die with sputtered nickel/gold metallization was placed on the surface of the silver stamp. The assembly was processed according to the following conditions: drying at 50° C. for 5 minutes, then drying at 140° C. for 30 minutes, and finally sintering at 300° C. and a pressure of 5 MPa for 2 minutes.

The formed joints were examined for voids by X-ray (see Figure 3, X-ray photo of the die attached to the copper heat sink) and by cross-sectional SEM observation (see Figure 4, showing the cross-section of the nanosilver joint). No voids were observed.

The reliability of silver contacts is assessed in thermal shock tests at temperatures between -50°C and +125°C. The joints formed with nanosilver paste successfully passed the test for 700 cycles.

Example 3

Nanogold slurries containing capped gold particles can be prepared as described in US Patent Application Serial No. 11/462,089. The slurry may include gold particles capped with about 1-2% by weight capping agent. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nano gold paste may be used to attach the die (or other electronic components) to the substrate.

Example 4

Nanoplatinum slurries containing capped platinum particles can be prepared as described in US Patent Application Serial No. 11/462,089. The slurry may include platinum microparticles capped with about 1-2% by weight capping agent. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nano-platinum paste can be used to attach the die (or other electronic components) to the substrate.

Example 5

Nanopalladium slurries containing capped palladium particles can be prepared as described in US Patent Application Serial No. 11/462,089. The slip may include palladium particles capped with about 1-2% by weight capping agent. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nano palladium paste can be used to attach the die (or other electronic components) to the substrate.

Example 6

Nano-copper pastes containing capped copper particles can be prepared as described in US Patent Application Serial No. 11/462,089. The slurry may include platinum microparticles capped with about 1-2% by weight capping agent. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nano copper paste can be used to attach the die (or other electronic components) to the substrate. During the attachment procedure, one or more sintering and/or drying steps may be performed under a nitrogen atmosphere.

Example 7

Nanosilver-nanocopper pastes containing silver particles and copper particles can be prepared as described in US Patent Application No. 11/462,089. The paste may include silver particles capped with about 1-2% by weight of capping agent or copper particles capped with about 1-2% by weight of capping agent or both. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nanosilver-nanocopper paste can be used to attach the die (or other electronic components) to the substrate. The nanosilver-nanocopper particles can be present in a ratio of 1:1, 2:1, 1:2, respectively, or any ratio between these ratios. During the attachment procedure, one or more sintering and/or drying steps may be performed under a nitrogen atmosphere.

Example 8

Nanosilver-nanogold pastes containing silver particles and gold particles can be prepared as described in US Patent Application No. 11/462,089. The paste may include silver particles capped with about 1-2% by weight of a capping agent or gold particles capped with about 1-2% by weight of a capping agent, or both. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nanosilver-nanogold paste can be used to attach the die (or other electronic components) to the substrate. Nanosilver-nanogold particles may be present in a ratio of 1:1, 2:1, 1:2, respectively, or any ratio between these ratios.

Example 9

A nanosilver-nanoplatinum paste comprising silver particles and platinum particles can be prepared as described in US Patent Application Serial No. 11/462,089. The slurry may include silver particles capped with about 1-2% by weight of capping agent or platinum particles capped with about 1-2% by weight of capping agent or both. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nanosilver-nanogold paste can be used to attach the die (or other electronic components) to the substrate. The nanosilver-nanoplatinum particles may be present in a ratio of 1:1, 2:1, 1:2, respectively, or any ratio between these ratios.

Example 10

Nanosilver-nanopalladium pastes containing silver particles and palladium particles can be prepared as described in US Patent Application No. 11/462,089. The slurry may include silver particles capped with about 1-2% by weight of capping agent or palladium particles capped with about 1-2% by weight of capping agent or both. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nanosilver-nanogold paste can be used to attach the die (or other electronic components) to the substrate. The particles of nanosilver-nanopalladium may be present in a ratio of 1:1, 2:1, 1:2 or any ratio between these ratios, respectively.

Example 11

A nanosilver-nanocopper-nanopalladium paste comprising silver particles, copper particles, and palladium particles can be prepared as described in US Patent Application No. 11/462,089. The paste may include silver particles capped with about 1-2% by weight of a capping agent, or copper particles capped with about 1-2% by weight of a capping agent or with about 1-2% by weight of a capping agent. % capping agent capped palladium microparticles or all three microparticles. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nano-silver-nano-copper-nano-palladium paste can be used to attach the die (or other electronic components) to the substrate. The nano-silver-nano-copper-nano-palladium particles may exist in a ratio of 1:1:1, 1:2:1, 1:1:2 or any ratio between these ratios, respectively. During the attachment procedure, one or more sintering and/or drying steps may be performed under a nitrogen atmosphere.

Example 12

A nanosilver-nanogold-nanopalladium paste comprising silver particles, gold particles and palladium particles can be prepared as described in US Patent Application No. 11/462,089. The slurry may include silver particles capped with about 1-2% by weight of a capping agent or gold particles capped with about 1-2% by weight of a capping agent or with about 1-2% by weight of a capping agent. The capping agent capped palladium microparticles or all three microparticles. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nano-silver-nano-gold-nano-palladium paste can be used to attach the die (or other electronic components) to the substrate. Nano-silver-nano-gold-nano-palladium particles may exist in a ratio of 1:1:1, 1:2:1, 1:1:2 or any ratio between these ratios.

Example 13

A nanosilver-nanoplatinum-nanopalladium paste comprising silver particles, platinum particles, and palladium particles can be prepared as described in US Patent Application No. 11/462,089. The slurry may include silver particles capped with about 1-2% by weight of capping agent or platinum particles capped with about 1-2% by weight of capping agent or about 1-2% by weight The capping agent capped palladium microparticles or all three microparticles. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nano-silver-nano-platinum-nano-palladium paste can be used to attach the die (or other electronic components) to the substrate. Nano-silver-nano-platinum-nano-palladium particles may exist in a ratio of 1:1:1, 1:2:1, 1:1:2 or any ratio between these ratios, respectively.

Example 14

A nanosilver-nanogold-nanocopper paste comprising silver particles, gold particles and copper particles can be prepared as described in US Patent Application No. 11/462,089. The slurry may include silver particles capped with about 1-2% by weight of a capping agent or gold particles capped with about 1-2% by weight of a capping agent or about 1-2% by weight The capping agent capped copper particles or all three particles. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. The nano-silver-nano-gold-nano-copper powder paste can be used to attach tube cores (or other electronic components) to substrates. Nano-silver-nano-gold-nano-copper particles can exist in a ratio of 1:1:1, 1:2:1, 1:1:2 or any ratio between these ratios. During the attachment procedure, one or more sintering and/or drying steps may be performed under a nitrogen atmosphere.

Those skilled in the art, given the reminder of this disclosure, will recognize that various components of these embodiments may be exchanged for or used in various compositions of other embodiments. partially replaced.

Although specific features, aspects, examples, and implementations have been described above, those of skill in the art, having been prompted by this disclosure, will readily recognize the disclosed illustrative features, aspects, examples, and and supplements, substitutions, modifications and changes of implementations.

Claims (24)

1. one kind makes the method for die attachment to the matrix, and this method comprises:

The nano material of end-blocking is arranged on the matrix;

Tube core is arranged on the arranged end-blocking nano material;

Dry arranged end-blocking nano material and arranged tube core; And

Under 300 ℃ or lower temperature, make through the arranged tube core of super-dry and through the end-blocking nano material sintering of super-dry die attachment to matrix.

2. according to the process of claim 1 wherein that the nano material of end-blocking comprises the silver-colored particulate of using the end-capping reagent end-blocking, wherein end-capping reagent occurs to the ratio of about 15wt.% with about 10wt.% based on the weight of end-blocking silver particulate.

3. according to the method for claim 2, further be included in silver-colored particulate with end-blocking be arranged on the matrix before earlier with the silver-colored microparticulate of end-blocking in solvent.

4. according to the method for claim 2, end-capping reagent is removed from end-blocking silver particulate during further being included in sintering step.

5. according to the process of claim 1 wherein that the nano material of end-blocking comprises the metal particle of end-blocking, wherein the metal of end-blocking metal particle is selected from gold, silver, copper, nickel, platinum, palladium, iron and alloy thereof.

6. according to the process of claim 1 wherein dry and sintering step is to finish 300 ℃ or lower temperature.

7. according to the process of claim 1 wherein that sintering step finishes in nitrogen atmosphere.

8. method according to Claim 8, wherein nitrogen atmosphere provides and equals atmospheric pressure in fact.

9. method according to Claim 8, wherein drying steps is finished under less than atmospheric pressure.

10. device, comprising: matrix; Be arranged in the tube core on the matrix; And the electric contact between tube core and the matrix, this electric contact is included in the nano material that 300 ℃ or lower sintering temperature provide the electric coupling between matrix and the tube core.

11. according to the device of claim 10, wherein matrix is a printed circuit board (PCB), and nano material comprises the silver-colored particulate of end-blocking.

12. according to the device of claim 11, wherein the silver-colored particulate of end-blocking comprised the end-capping reagent of about 1-3wt.% based on the weight of nano material (end-blocking silver particulate) before forming contact.

13. according to the device of claim 10, wherein nano material comprises metal particle, wherein the metal of metal particle is selected from gold, silver, copper, nickel, platinum, palladium, iron and alloy thereof.

14. according to the device of claim 10, wherein electric contact has unified in fact thickness between tube core and matrix.

15. according to the device of claim 10, wherein electric contact comes down to void-free.

16. complete articles for use of producing electric contact, these complete articles for use comprise:

Nano material, this nano material comprises about 10wt.% by the weight based on nano material and forms to the end-blocking metal particle of the end-capping reagent of about 15wt.%;

Use nano material at matrix be arranged in the instruction that electric contact is provided between the tube core on the matrix.

17. the complete articles for use according to claim 16 further comprise the tube core that uses with nano material.

18. the complete articles for use according to claim 17 further comprise the matrix that uses with tube core and nano material.

19. according to the complete articles for use of claim 18, wherein matrix is a printed circuit board (PCB).

20. a method of facilitating tube core and matrix electric coupling, this method comprises: providing provides the electric contact effectively nano material between tube core and matrix after nano material sintering under 300 ℃ or lower temperature.

21. according to the method for claim 20, wherein nano material is effective to electric contact is provided between tube core and matrix after the sintering under pressure below atmospheric pressure.

22. according to the method for claim 21, wherein nano material comprises the silver-colored particulate of end-blocking, the silver-colored particulate of this end-blocking has the end-capping reagent of about 10wt.% to about 15wt.% based on the weight of end-blocking silver particulate.

23. according to the method for claim 21, wherein nano material comprises metal particle, wherein the metal of metal particle is selected from gold, silver, copper, nickel, platinum, palladium, iron and alloy thereof.

24. according to the method for claim 23, wherein metal particle is with the end-capping reagent end-blocking that is selected from the sulphur alkohol and amine.

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